The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_tc.c

Version: -  FREEBSD  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-2  -  FREEBSD-11-1  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-4  -  FREEBSD-10-3  -  FREEBSD-10-2  -  FREEBSD-10-1  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-3  -  FREEBSD-9-2  -  FREEBSD-9-1  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-4  -  FREEBSD-8-3  -  FREEBSD-8-2  -  FREEBSD-8-1  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-4  -  FREEBSD-7-3  -  FREEBSD-7-2  -  FREEBSD-7-1  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-4  -  FREEBSD-6-3  -  FREEBSD-6-2  -  FREEBSD-6-1  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-5  -  FREEBSD-5-4  -  FREEBSD-5-3  -  FREEBSD-5-2  -  FREEBSD-5-1  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  linux-2.6  -  linux-2.4.22  -  MK83  -  MK84  -  PLAN9  -  DFBSD  -  NETBSD  -  NETBSD5  -  NETBSD4  -  NETBSD3  -  NETBSD20  -  OPENBSD  -  xnu-517  -  xnu-792  -  xnu-792.6.70  -  xnu-1228  -  xnu-1456.1.26  -  xnu-1699.24.8  -  xnu-2050.18.24  -  OPENSOLARIS  -  minix-3-1-1 
SearchContext: -  none  -  3  -  10 

    1 /*-
    2  * ----------------------------------------------------------------------------
    3  * "THE BEER-WARE LICENSE" (Revision 42):
    4  * <phk@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
    5  * can do whatever you want with this stuff. If we meet some day, and you think
    6  * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
    7  * ----------------------------------------------------------------------------
    8  *
    9  * Copyright (c) 2011 The FreeBSD Foundation
   10  * All rights reserved.
   11  *
   12  * Portions of this software were developed by Julien Ridoux at the University
   13  * of Melbourne under sponsorship from the FreeBSD Foundation.
   14  */
   15 
   16 #include <sys/cdefs.h>
   17 __FBSDID("$FreeBSD: releng/10.1/sys/kern/kern_tc.c 247777 2013-03-04 11:09:56Z davide $");
   18 
   19 #include "opt_compat.h"
   20 #include "opt_ntp.h"
   21 #include "opt_ffclock.h"
   22 
   23 #include <sys/param.h>
   24 #include <sys/kernel.h>
   25 #include <sys/limits.h>
   26 #ifdef FFCLOCK
   27 #include <sys/lock.h>
   28 #include <sys/mutex.h>
   29 #endif
   30 #include <sys/sysctl.h>
   31 #include <sys/syslog.h>
   32 #include <sys/systm.h>
   33 #include <sys/timeffc.h>
   34 #include <sys/timepps.h>
   35 #include <sys/timetc.h>
   36 #include <sys/timex.h>
   37 #include <sys/vdso.h>
   38 
   39 /*
   40  * A large step happens on boot.  This constant detects such steps.
   41  * It is relatively small so that ntp_update_second gets called enough
   42  * in the typical 'missed a couple of seconds' case, but doesn't loop
   43  * forever when the time step is large.
   44  */
   45 #define LARGE_STEP      200
   46 
   47 /*
   48  * Implement a dummy timecounter which we can use until we get a real one
   49  * in the air.  This allows the console and other early stuff to use
   50  * time services.
   51  */
   52 
   53 static u_int
   54 dummy_get_timecount(struct timecounter *tc)
   55 {
   56         static u_int now;
   57 
   58         return (++now);
   59 }
   60 
   61 static struct timecounter dummy_timecounter = {
   62         dummy_get_timecount, 0, ~0u, 1000000, "dummy", -1000000
   63 };
   64 
   65 struct timehands {
   66         /* These fields must be initialized by the driver. */
   67         struct timecounter      *th_counter;
   68         int64_t                 th_adjustment;
   69         uint64_t                th_scale;
   70         u_int                   th_offset_count;
   71         struct bintime          th_offset;
   72         struct timeval          th_microtime;
   73         struct timespec         th_nanotime;
   74         /* Fields not to be copied in tc_windup start with th_generation. */
   75         volatile u_int          th_generation;
   76         struct timehands        *th_next;
   77 };
   78 
   79 static struct timehands th0;
   80 static struct timehands th9 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th0};
   81 static struct timehands th8 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th9};
   82 static struct timehands th7 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th8};
   83 static struct timehands th6 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th7};
   84 static struct timehands th5 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th6};
   85 static struct timehands th4 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th5};
   86 static struct timehands th3 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th4};
   87 static struct timehands th2 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th3};
   88 static struct timehands th1 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th2};
   89 static struct timehands th0 = {
   90         &dummy_timecounter,
   91         0,
   92         (uint64_t)-1 / 1000000,
   93         0,
   94         {1, 0},
   95         {0, 0},
   96         {0, 0},
   97         1,
   98         &th1
   99 };
  100 
  101 static struct timehands *volatile timehands = &th0;
  102 struct timecounter *timecounter = &dummy_timecounter;
  103 static struct timecounter *timecounters = &dummy_timecounter;
  104 
  105 int tc_min_ticktock_freq = 1;
  106 
  107 volatile time_t time_second = 1;
  108 volatile time_t time_uptime = 1;
  109 
  110 struct bintime boottimebin;
  111 struct timeval boottime;
  112 static int sysctl_kern_boottime(SYSCTL_HANDLER_ARGS);
  113 SYSCTL_PROC(_kern, KERN_BOOTTIME, boottime, CTLTYPE_STRUCT|CTLFLAG_RD,
  114     NULL, 0, sysctl_kern_boottime, "S,timeval", "System boottime");
  115 
  116 SYSCTL_NODE(_kern, OID_AUTO, timecounter, CTLFLAG_RW, 0, "");
  117 static SYSCTL_NODE(_kern_timecounter, OID_AUTO, tc, CTLFLAG_RW, 0, "");
  118 
  119 static int timestepwarnings;
  120 SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RW,
  121     &timestepwarnings, 0, "Log time steps");
  122 
  123 struct bintime bt_timethreshold;
  124 struct bintime bt_tickthreshold;
  125 sbintime_t sbt_timethreshold;
  126 sbintime_t sbt_tickthreshold;
  127 struct bintime tc_tick_bt;
  128 sbintime_t tc_tick_sbt;
  129 int tc_precexp;
  130 int tc_timepercentage = TC_DEFAULTPERC;
  131 TUNABLE_INT("kern.timecounter.alloweddeviation", &tc_timepercentage);
  132 static int sysctl_kern_timecounter_adjprecision(SYSCTL_HANDLER_ARGS);
  133 SYSCTL_PROC(_kern_timecounter, OID_AUTO, alloweddeviation,
  134     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0,
  135     sysctl_kern_timecounter_adjprecision, "I",
  136     "Allowed time interval deviation in percents");
  137 
  138 static void tc_windup(void);
  139 static void cpu_tick_calibrate(int);
  140 
  141 void dtrace_getnanotime(struct timespec *tsp);
  142 
  143 static int
  144 sysctl_kern_boottime(SYSCTL_HANDLER_ARGS)
  145 {
  146 #ifndef __mips__
  147 #ifdef SCTL_MASK32
  148         int tv[2];
  149 
  150         if (req->flags & SCTL_MASK32) {
  151                 tv[0] = boottime.tv_sec;
  152                 tv[1] = boottime.tv_usec;
  153                 return SYSCTL_OUT(req, tv, sizeof(tv));
  154         } else
  155 #endif
  156 #endif
  157                 return SYSCTL_OUT(req, &boottime, sizeof(boottime));
  158 }
  159 
  160 static int
  161 sysctl_kern_timecounter_get(SYSCTL_HANDLER_ARGS)
  162 {
  163         u_int ncount;
  164         struct timecounter *tc = arg1;
  165 
  166         ncount = tc->tc_get_timecount(tc);
  167         return sysctl_handle_int(oidp, &ncount, 0, req);
  168 }
  169 
  170 static int
  171 sysctl_kern_timecounter_freq(SYSCTL_HANDLER_ARGS)
  172 {
  173         uint64_t freq;
  174         struct timecounter *tc = arg1;
  175 
  176         freq = tc->tc_frequency;
  177         return sysctl_handle_64(oidp, &freq, 0, req);
  178 }
  179 
  180 /*
  181  * Return the difference between the timehands' counter value now and what
  182  * was when we copied it to the timehands' offset_count.
  183  */
  184 static __inline u_int
  185 tc_delta(struct timehands *th)
  186 {
  187         struct timecounter *tc;
  188 
  189         tc = th->th_counter;
  190         return ((tc->tc_get_timecount(tc) - th->th_offset_count) &
  191             tc->tc_counter_mask);
  192 }
  193 
  194 /*
  195  * Functions for reading the time.  We have to loop until we are sure that
  196  * the timehands that we operated on was not updated under our feet.  See
  197  * the comment in <sys/time.h> for a description of these 12 functions.
  198  */
  199 
  200 #ifdef FFCLOCK
  201 void
  202 fbclock_binuptime(struct bintime *bt)
  203 {
  204         struct timehands *th;
  205         unsigned int gen;
  206 
  207         do {
  208                 th = timehands;
  209                 gen = th->th_generation;
  210                 *bt = th->th_offset;
  211                 bintime_addx(bt, th->th_scale * tc_delta(th));
  212         } while (gen == 0 || gen != th->th_generation);
  213 }
  214 
  215 void
  216 fbclock_nanouptime(struct timespec *tsp)
  217 {
  218         struct bintime bt;
  219 
  220         fbclock_binuptime(&bt);
  221         bintime2timespec(&bt, tsp);
  222 }
  223 
  224 void
  225 fbclock_microuptime(struct timeval *tvp)
  226 {
  227         struct bintime bt;
  228 
  229         fbclock_binuptime(&bt);
  230         bintime2timeval(&bt, tvp);
  231 }
  232 
  233 void
  234 fbclock_bintime(struct bintime *bt)
  235 {
  236 
  237         fbclock_binuptime(bt);
  238         bintime_add(bt, &boottimebin);
  239 }
  240 
  241 void
  242 fbclock_nanotime(struct timespec *tsp)
  243 {
  244         struct bintime bt;
  245 
  246         fbclock_bintime(&bt);
  247         bintime2timespec(&bt, tsp);
  248 }
  249 
  250 void
  251 fbclock_microtime(struct timeval *tvp)
  252 {
  253         struct bintime bt;
  254 
  255         fbclock_bintime(&bt);
  256         bintime2timeval(&bt, tvp);
  257 }
  258 
  259 void
  260 fbclock_getbinuptime(struct bintime *bt)
  261 {
  262         struct timehands *th;
  263         unsigned int gen;
  264 
  265         do {
  266                 th = timehands;
  267                 gen = th->th_generation;
  268                 *bt = th->th_offset;
  269         } while (gen == 0 || gen != th->th_generation);
  270 }
  271 
  272 void
  273 fbclock_getnanouptime(struct timespec *tsp)
  274 {
  275         struct timehands *th;
  276         unsigned int gen;
  277 
  278         do {
  279                 th = timehands;
  280                 gen = th->th_generation;
  281                 bintime2timespec(&th->th_offset, tsp);
  282         } while (gen == 0 || gen != th->th_generation);
  283 }
  284 
  285 void
  286 fbclock_getmicrouptime(struct timeval *tvp)
  287 {
  288         struct timehands *th;
  289         unsigned int gen;
  290 
  291         do {
  292                 th = timehands;
  293                 gen = th->th_generation;
  294                 bintime2timeval(&th->th_offset, tvp);
  295         } while (gen == 0 || gen != th->th_generation);
  296 }
  297 
  298 void
  299 fbclock_getbintime(struct bintime *bt)
  300 {
  301         struct timehands *th;
  302         unsigned int gen;
  303 
  304         do {
  305                 th = timehands;
  306                 gen = th->th_generation;
  307                 *bt = th->th_offset;
  308         } while (gen == 0 || gen != th->th_generation);
  309         bintime_add(bt, &boottimebin);
  310 }
  311 
  312 void
  313 fbclock_getnanotime(struct timespec *tsp)
  314 {
  315         struct timehands *th;
  316         unsigned int gen;
  317 
  318         do {
  319                 th = timehands;
  320                 gen = th->th_generation;
  321                 *tsp = th->th_nanotime;
  322         } while (gen == 0 || gen != th->th_generation);
  323 }
  324 
  325 void
  326 fbclock_getmicrotime(struct timeval *tvp)
  327 {
  328         struct timehands *th;
  329         unsigned int gen;
  330 
  331         do {
  332                 th = timehands;
  333                 gen = th->th_generation;
  334                 *tvp = th->th_microtime;
  335         } while (gen == 0 || gen != th->th_generation);
  336 }
  337 #else /* !FFCLOCK */
  338 void
  339 binuptime(struct bintime *bt)
  340 {
  341         struct timehands *th;
  342         u_int gen;
  343 
  344         do {
  345                 th = timehands;
  346                 gen = th->th_generation;
  347                 *bt = th->th_offset;
  348                 bintime_addx(bt, th->th_scale * tc_delta(th));
  349         } while (gen == 0 || gen != th->th_generation);
  350 }
  351 
  352 void
  353 nanouptime(struct timespec *tsp)
  354 {
  355         struct bintime bt;
  356 
  357         binuptime(&bt);
  358         bintime2timespec(&bt, tsp);
  359 }
  360 
  361 void
  362 microuptime(struct timeval *tvp)
  363 {
  364         struct bintime bt;
  365 
  366         binuptime(&bt);
  367         bintime2timeval(&bt, tvp);
  368 }
  369 
  370 void
  371 bintime(struct bintime *bt)
  372 {
  373 
  374         binuptime(bt);
  375         bintime_add(bt, &boottimebin);
  376 }
  377 
  378 void
  379 nanotime(struct timespec *tsp)
  380 {
  381         struct bintime bt;
  382 
  383         bintime(&bt);
  384         bintime2timespec(&bt, tsp);
  385 }
  386 
  387 void
  388 microtime(struct timeval *tvp)
  389 {
  390         struct bintime bt;
  391 
  392         bintime(&bt);
  393         bintime2timeval(&bt, tvp);
  394 }
  395 
  396 void
  397 getbinuptime(struct bintime *bt)
  398 {
  399         struct timehands *th;
  400         u_int gen;
  401 
  402         do {
  403                 th = timehands;
  404                 gen = th->th_generation;
  405                 *bt = th->th_offset;
  406         } while (gen == 0 || gen != th->th_generation);
  407 }
  408 
  409 void
  410 getnanouptime(struct timespec *tsp)
  411 {
  412         struct timehands *th;
  413         u_int gen;
  414 
  415         do {
  416                 th = timehands;
  417                 gen = th->th_generation;
  418                 bintime2timespec(&th->th_offset, tsp);
  419         } while (gen == 0 || gen != th->th_generation);
  420 }
  421 
  422 void
  423 getmicrouptime(struct timeval *tvp)
  424 {
  425         struct timehands *th;
  426         u_int gen;
  427 
  428         do {
  429                 th = timehands;
  430                 gen = th->th_generation;
  431                 bintime2timeval(&th->th_offset, tvp);
  432         } while (gen == 0 || gen != th->th_generation);
  433 }
  434 
  435 void
  436 getbintime(struct bintime *bt)
  437 {
  438         struct timehands *th;
  439         u_int gen;
  440 
  441         do {
  442                 th = timehands;
  443                 gen = th->th_generation;
  444                 *bt = th->th_offset;
  445         } while (gen == 0 || gen != th->th_generation);
  446         bintime_add(bt, &boottimebin);
  447 }
  448 
  449 void
  450 getnanotime(struct timespec *tsp)
  451 {
  452         struct timehands *th;
  453         u_int gen;
  454 
  455         do {
  456                 th = timehands;
  457                 gen = th->th_generation;
  458                 *tsp = th->th_nanotime;
  459         } while (gen == 0 || gen != th->th_generation);
  460 }
  461 
  462 void
  463 getmicrotime(struct timeval *tvp)
  464 {
  465         struct timehands *th;
  466         u_int gen;
  467 
  468         do {
  469                 th = timehands;
  470                 gen = th->th_generation;
  471                 *tvp = th->th_microtime;
  472         } while (gen == 0 || gen != th->th_generation);
  473 }
  474 #endif /* FFCLOCK */
  475 
  476 #ifdef FFCLOCK
  477 /*
  478  * Support for feed-forward synchronization algorithms. This is heavily inspired
  479  * by the timehands mechanism but kept independent from it. *_windup() functions
  480  * have some connection to avoid accessing the timecounter hardware more than
  481  * necessary.
  482  */
  483 
  484 /* Feed-forward clock estimates kept updated by the synchronization daemon. */
  485 struct ffclock_estimate ffclock_estimate;
  486 struct bintime ffclock_boottime;        /* Feed-forward boot time estimate. */
  487 uint32_t ffclock_status;                /* Feed-forward clock status. */
  488 int8_t ffclock_updated;                 /* New estimates are available. */
  489 struct mtx ffclock_mtx;                 /* Mutex on ffclock_estimate. */
  490 
  491 struct fftimehands {
  492         struct ffclock_estimate cest;
  493         struct bintime          tick_time;
  494         struct bintime          tick_time_lerp;
  495         ffcounter               tick_ffcount;
  496         uint64_t                period_lerp;
  497         volatile uint8_t        gen;
  498         struct fftimehands      *next;
  499 };
  500 
  501 #define NUM_ELEMENTS(x) (sizeof(x) / sizeof(*x))
  502 
  503 static struct fftimehands ffth[10];
  504 static struct fftimehands *volatile fftimehands = ffth;
  505 
  506 static void
  507 ffclock_init(void)
  508 {
  509         struct fftimehands *cur;
  510         struct fftimehands *last;
  511 
  512         memset(ffth, 0, sizeof(ffth));
  513 
  514         last = ffth + NUM_ELEMENTS(ffth) - 1;
  515         for (cur = ffth; cur < last; cur++)
  516                 cur->next = cur + 1;
  517         last->next = ffth;
  518 
  519         ffclock_updated = 0;
  520         ffclock_status = FFCLOCK_STA_UNSYNC;
  521         mtx_init(&ffclock_mtx, "ffclock lock", NULL, MTX_DEF);
  522 }
  523 
  524 /*
  525  * Reset the feed-forward clock estimates. Called from inittodr() to get things
  526  * kick started and uses the timecounter nominal frequency as a first period
  527  * estimate. Note: this function may be called several time just after boot.
  528  * Note: this is the only function that sets the value of boot time for the
  529  * monotonic (i.e. uptime) version of the feed-forward clock.
  530  */
  531 void
  532 ffclock_reset_clock(struct timespec *ts)
  533 {
  534         struct timecounter *tc;
  535         struct ffclock_estimate cest;
  536 
  537         tc = timehands->th_counter;
  538         memset(&cest, 0, sizeof(struct ffclock_estimate));
  539 
  540         timespec2bintime(ts, &ffclock_boottime);
  541         timespec2bintime(ts, &(cest.update_time));
  542         ffclock_read_counter(&cest.update_ffcount);
  543         cest.leapsec_next = 0;
  544         cest.period = ((1ULL << 63) / tc->tc_frequency) << 1;
  545         cest.errb_abs = 0;
  546         cest.errb_rate = 0;
  547         cest.status = FFCLOCK_STA_UNSYNC;
  548         cest.leapsec_total = 0;
  549         cest.leapsec = 0;
  550 
  551         mtx_lock(&ffclock_mtx);
  552         bcopy(&cest, &ffclock_estimate, sizeof(struct ffclock_estimate));
  553         ffclock_updated = INT8_MAX;
  554         mtx_unlock(&ffclock_mtx);
  555 
  556         printf("ffclock reset: %s (%llu Hz), time = %ld.%09lu\n", tc->tc_name,
  557             (unsigned long long)tc->tc_frequency, (long)ts->tv_sec,
  558             (unsigned long)ts->tv_nsec);
  559 }
  560 
  561 /*
  562  * Sub-routine to convert a time interval measured in RAW counter units to time
  563  * in seconds stored in bintime format.
  564  * NOTE: bintime_mul requires u_int, but the value of the ffcounter may be
  565  * larger than the max value of u_int (on 32 bit architecture). Loop to consume
  566  * extra cycles.
  567  */
  568 static void
  569 ffclock_convert_delta(ffcounter ffdelta, uint64_t period, struct bintime *bt)
  570 {
  571         struct bintime bt2;
  572         ffcounter delta, delta_max;
  573 
  574         delta_max = (1ULL << (8 * sizeof(unsigned int))) - 1;
  575         bintime_clear(bt);
  576         do {
  577                 if (ffdelta > delta_max)
  578                         delta = delta_max;
  579                 else
  580                         delta = ffdelta;
  581                 bt2.sec = 0;
  582                 bt2.frac = period;
  583                 bintime_mul(&bt2, (unsigned int)delta);
  584                 bintime_add(bt, &bt2);
  585                 ffdelta -= delta;
  586         } while (ffdelta > 0);
  587 }
  588 
  589 /*
  590  * Update the fftimehands.
  591  * Push the tick ffcount and time(s) forward based on current clock estimate.
  592  * The conversion from ffcounter to bintime relies on the difference clock
  593  * principle, whose accuracy relies on computing small time intervals. If a new
  594  * clock estimate has been passed by the synchronisation daemon, make it
  595  * current, and compute the linear interpolation for monotonic time if needed.
  596  */
  597 static void
  598 ffclock_windup(unsigned int delta)
  599 {
  600         struct ffclock_estimate *cest;
  601         struct fftimehands *ffth;
  602         struct bintime bt, gap_lerp;
  603         ffcounter ffdelta;
  604         uint64_t frac;
  605         unsigned int polling;
  606         uint8_t forward_jump, ogen;
  607 
  608         /*
  609          * Pick the next timehand, copy current ffclock estimates and move tick
  610          * times and counter forward.
  611          */
  612         forward_jump = 0;
  613         ffth = fftimehands->next;
  614         ogen = ffth->gen;
  615         ffth->gen = 0;
  616         cest = &ffth->cest;
  617         bcopy(&fftimehands->cest, cest, sizeof(struct ffclock_estimate));
  618         ffdelta = (ffcounter)delta;
  619         ffth->period_lerp = fftimehands->period_lerp;
  620 
  621         ffth->tick_time = fftimehands->tick_time;
  622         ffclock_convert_delta(ffdelta, cest->period, &bt);
  623         bintime_add(&ffth->tick_time, &bt);
  624 
  625         ffth->tick_time_lerp = fftimehands->tick_time_lerp;
  626         ffclock_convert_delta(ffdelta, ffth->period_lerp, &bt);
  627         bintime_add(&ffth->tick_time_lerp, &bt);
  628 
  629         ffth->tick_ffcount = fftimehands->tick_ffcount + ffdelta;
  630 
  631         /*
  632          * Assess the status of the clock, if the last update is too old, it is
  633          * likely the synchronisation daemon is dead and the clock is free
  634          * running.
  635          */
  636         if (ffclock_updated == 0) {
  637                 ffdelta = ffth->tick_ffcount - cest->update_ffcount;
  638                 ffclock_convert_delta(ffdelta, cest->period, &bt);
  639                 if (bt.sec > 2 * FFCLOCK_SKM_SCALE)
  640                         ffclock_status |= FFCLOCK_STA_UNSYNC;
  641         }
  642 
  643         /*
  644          * If available, grab updated clock estimates and make them current.
  645          * Recompute time at this tick using the updated estimates. The clock
  646          * estimates passed the feed-forward synchronisation daemon may result
  647          * in time conversion that is not monotonically increasing (just after
  648          * the update). time_lerp is a particular linear interpolation over the
  649          * synchronisation algo polling period that ensures monotonicity for the
  650          * clock ids requesting it.
  651          */
  652         if (ffclock_updated > 0) {
  653                 bcopy(&ffclock_estimate, cest, sizeof(struct ffclock_estimate));
  654                 ffdelta = ffth->tick_ffcount - cest->update_ffcount;
  655                 ffth->tick_time = cest->update_time;
  656                 ffclock_convert_delta(ffdelta, cest->period, &bt);
  657                 bintime_add(&ffth->tick_time, &bt);
  658 
  659                 /* ffclock_reset sets ffclock_updated to INT8_MAX */
  660                 if (ffclock_updated == INT8_MAX)
  661                         ffth->tick_time_lerp = ffth->tick_time;
  662 
  663                 if (bintime_cmp(&ffth->tick_time, &ffth->tick_time_lerp, >))
  664                         forward_jump = 1;
  665                 else
  666                         forward_jump = 0;
  667 
  668                 bintime_clear(&gap_lerp);
  669                 if (forward_jump) {
  670                         gap_lerp = ffth->tick_time;
  671                         bintime_sub(&gap_lerp, &ffth->tick_time_lerp);
  672                 } else {
  673                         gap_lerp = ffth->tick_time_lerp;
  674                         bintime_sub(&gap_lerp, &ffth->tick_time);
  675                 }
  676 
  677                 /*
  678                  * The reset from the RTC clock may be far from accurate, and
  679                  * reducing the gap between real time and interpolated time
  680                  * could take a very long time if the interpolated clock insists
  681                  * on strict monotonicity. The clock is reset under very strict
  682                  * conditions (kernel time is known to be wrong and
  683                  * synchronization daemon has been restarted recently.
  684                  * ffclock_boottime absorbs the jump to ensure boot time is
  685                  * correct and uptime functions stay consistent.
  686                  */
  687                 if (((ffclock_status & FFCLOCK_STA_UNSYNC) == FFCLOCK_STA_UNSYNC) &&
  688                     ((cest->status & FFCLOCK_STA_UNSYNC) == 0) &&
  689                     ((cest->status & FFCLOCK_STA_WARMUP) == FFCLOCK_STA_WARMUP)) {
  690                         if (forward_jump)
  691                                 bintime_add(&ffclock_boottime, &gap_lerp);
  692                         else
  693                                 bintime_sub(&ffclock_boottime, &gap_lerp);
  694                         ffth->tick_time_lerp = ffth->tick_time;
  695                         bintime_clear(&gap_lerp);
  696                 }
  697 
  698                 ffclock_status = cest->status;
  699                 ffth->period_lerp = cest->period;
  700 
  701                 /*
  702                  * Compute corrected period used for the linear interpolation of
  703                  * time. The rate of linear interpolation is capped to 5000PPM
  704                  * (5ms/s).
  705                  */
  706                 if (bintime_isset(&gap_lerp)) {
  707                         ffdelta = cest->update_ffcount;
  708                         ffdelta -= fftimehands->cest.update_ffcount;
  709                         ffclock_convert_delta(ffdelta, cest->period, &bt);
  710                         polling = bt.sec;
  711                         bt.sec = 0;
  712                         bt.frac = 5000000 * (uint64_t)18446744073LL;
  713                         bintime_mul(&bt, polling);
  714                         if (bintime_cmp(&gap_lerp, &bt, >))
  715                                 gap_lerp = bt;
  716 
  717                         /* Approximate 1 sec by 1-(1/2^64) to ease arithmetic */
  718                         frac = 0;
  719                         if (gap_lerp.sec > 0) {
  720                                 frac -= 1;
  721                                 frac /= ffdelta / gap_lerp.sec;
  722                         }
  723                         frac += gap_lerp.frac / ffdelta;
  724 
  725                         if (forward_jump)
  726                                 ffth->period_lerp += frac;
  727                         else
  728                                 ffth->period_lerp -= frac;
  729                 }
  730 
  731                 ffclock_updated = 0;
  732         }
  733         if (++ogen == 0)
  734                 ogen = 1;
  735         ffth->gen = ogen;
  736         fftimehands = ffth;
  737 }
  738 
  739 /*
  740  * Adjust the fftimehands when the timecounter is changed. Stating the obvious,
  741  * the old and new hardware counter cannot be read simultaneously. tc_windup()
  742  * does read the two counters 'back to back', but a few cycles are effectively
  743  * lost, and not accumulated in tick_ffcount. This is a fairly radical
  744  * operation for a feed-forward synchronization daemon, and it is its job to not
  745  * pushing irrelevant data to the kernel. Because there is no locking here,
  746  * simply force to ignore pending or next update to give daemon a chance to
  747  * realize the counter has changed.
  748  */
  749 static void
  750 ffclock_change_tc(struct timehands *th)
  751 {
  752         struct fftimehands *ffth;
  753         struct ffclock_estimate *cest;
  754         struct timecounter *tc;
  755         uint8_t ogen;
  756 
  757         tc = th->th_counter;
  758         ffth = fftimehands->next;
  759         ogen = ffth->gen;
  760         ffth->gen = 0;
  761 
  762         cest = &ffth->cest;
  763         bcopy(&(fftimehands->cest), cest, sizeof(struct ffclock_estimate));
  764         cest->period = ((1ULL << 63) / tc->tc_frequency ) << 1;
  765         cest->errb_abs = 0;
  766         cest->errb_rate = 0;
  767         cest->status |= FFCLOCK_STA_UNSYNC;
  768 
  769         ffth->tick_ffcount = fftimehands->tick_ffcount;
  770         ffth->tick_time_lerp = fftimehands->tick_time_lerp;
  771         ffth->tick_time = fftimehands->tick_time;
  772         ffth->period_lerp = cest->period;
  773 
  774         /* Do not lock but ignore next update from synchronization daemon. */
  775         ffclock_updated--;
  776 
  777         if (++ogen == 0)
  778                 ogen = 1;
  779         ffth->gen = ogen;
  780         fftimehands = ffth;
  781 }
  782 
  783 /*
  784  * Retrieve feed-forward counter and time of last kernel tick.
  785  */
  786 void
  787 ffclock_last_tick(ffcounter *ffcount, struct bintime *bt, uint32_t flags)
  788 {
  789         struct fftimehands *ffth;
  790         uint8_t gen;
  791 
  792         /*
  793          * No locking but check generation has not changed. Also need to make
  794          * sure ffdelta is positive, i.e. ffcount > tick_ffcount.
  795          */
  796         do {
  797                 ffth = fftimehands;
  798                 gen = ffth->gen;
  799                 if ((flags & FFCLOCK_LERP) == FFCLOCK_LERP)
  800                         *bt = ffth->tick_time_lerp;
  801                 else
  802                         *bt = ffth->tick_time;
  803                 *ffcount = ffth->tick_ffcount;
  804         } while (gen == 0 || gen != ffth->gen);
  805 }
  806 
  807 /*
  808  * Absolute clock conversion. Low level function to convert ffcounter to
  809  * bintime. The ffcounter is converted using the current ffclock period estimate
  810  * or the "interpolated period" to ensure monotonicity.
  811  * NOTE: this conversion may have been deferred, and the clock updated since the
  812  * hardware counter has been read.
  813  */
  814 void
  815 ffclock_convert_abs(ffcounter ffcount, struct bintime *bt, uint32_t flags)
  816 {
  817         struct fftimehands *ffth;
  818         struct bintime bt2;
  819         ffcounter ffdelta;
  820         uint8_t gen;
  821 
  822         /*
  823          * No locking but check generation has not changed. Also need to make
  824          * sure ffdelta is positive, i.e. ffcount > tick_ffcount.
  825          */
  826         do {
  827                 ffth = fftimehands;
  828                 gen = ffth->gen;
  829                 if (ffcount > ffth->tick_ffcount)
  830                         ffdelta = ffcount - ffth->tick_ffcount;
  831                 else
  832                         ffdelta = ffth->tick_ffcount - ffcount;
  833 
  834                 if ((flags & FFCLOCK_LERP) == FFCLOCK_LERP) {
  835                         *bt = ffth->tick_time_lerp;
  836                         ffclock_convert_delta(ffdelta, ffth->period_lerp, &bt2);
  837                 } else {
  838                         *bt = ffth->tick_time;
  839                         ffclock_convert_delta(ffdelta, ffth->cest.period, &bt2);
  840                 }
  841 
  842                 if (ffcount > ffth->tick_ffcount)
  843                         bintime_add(bt, &bt2);
  844                 else
  845                         bintime_sub(bt, &bt2);
  846         } while (gen == 0 || gen != ffth->gen);
  847 }
  848 
  849 /*
  850  * Difference clock conversion.
  851  * Low level function to Convert a time interval measured in RAW counter units
  852  * into bintime. The difference clock allows measuring small intervals much more
  853  * reliably than the absolute clock.
  854  */
  855 void
  856 ffclock_convert_diff(ffcounter ffdelta, struct bintime *bt)
  857 {
  858         struct fftimehands *ffth;
  859         uint8_t gen;
  860 
  861         /* No locking but check generation has not changed. */
  862         do {
  863                 ffth = fftimehands;
  864                 gen = ffth->gen;
  865                 ffclock_convert_delta(ffdelta, ffth->cest.period, bt);
  866         } while (gen == 0 || gen != ffth->gen);
  867 }
  868 
  869 /*
  870  * Access to current ffcounter value.
  871  */
  872 void
  873 ffclock_read_counter(ffcounter *ffcount)
  874 {
  875         struct timehands *th;
  876         struct fftimehands *ffth;
  877         unsigned int gen, delta;
  878 
  879         /*
  880          * ffclock_windup() called from tc_windup(), safe to rely on
  881          * th->th_generation only, for correct delta and ffcounter.
  882          */
  883         do {
  884                 th = timehands;
  885                 gen = th->th_generation;
  886                 ffth = fftimehands;
  887                 delta = tc_delta(th);
  888                 *ffcount = ffth->tick_ffcount;
  889         } while (gen == 0 || gen != th->th_generation);
  890 
  891         *ffcount += delta;
  892 }
  893 
  894 void
  895 binuptime(struct bintime *bt)
  896 {
  897 
  898         binuptime_fromclock(bt, sysclock_active);
  899 }
  900 
  901 void
  902 nanouptime(struct timespec *tsp)
  903 {
  904 
  905         nanouptime_fromclock(tsp, sysclock_active);
  906 }
  907 
  908 void
  909 microuptime(struct timeval *tvp)
  910 {
  911 
  912         microuptime_fromclock(tvp, sysclock_active);
  913 }
  914 
  915 void
  916 bintime(struct bintime *bt)
  917 {
  918 
  919         bintime_fromclock(bt, sysclock_active);
  920 }
  921 
  922 void
  923 nanotime(struct timespec *tsp)
  924 {
  925 
  926         nanotime_fromclock(tsp, sysclock_active);
  927 }
  928 
  929 void
  930 microtime(struct timeval *tvp)
  931 {
  932 
  933         microtime_fromclock(tvp, sysclock_active);
  934 }
  935 
  936 void
  937 getbinuptime(struct bintime *bt)
  938 {
  939 
  940         getbinuptime_fromclock(bt, sysclock_active);
  941 }
  942 
  943 void
  944 getnanouptime(struct timespec *tsp)
  945 {
  946 
  947         getnanouptime_fromclock(tsp, sysclock_active);
  948 }
  949 
  950 void
  951 getmicrouptime(struct timeval *tvp)
  952 {
  953 
  954         getmicrouptime_fromclock(tvp, sysclock_active);
  955 }
  956 
  957 void
  958 getbintime(struct bintime *bt)
  959 {
  960 
  961         getbintime_fromclock(bt, sysclock_active);
  962 }
  963 
  964 void
  965 getnanotime(struct timespec *tsp)
  966 {
  967 
  968         getnanotime_fromclock(tsp, sysclock_active);
  969 }
  970 
  971 void
  972 getmicrotime(struct timeval *tvp)
  973 {
  974 
  975         getmicrouptime_fromclock(tvp, sysclock_active);
  976 }
  977 
  978 #endif /* FFCLOCK */
  979 
  980 /*
  981  * This is a clone of getnanotime and used for walltimestamps.
  982  * The dtrace_ prefix prevents fbt from creating probes for
  983  * it so walltimestamp can be safely used in all fbt probes.
  984  */
  985 void
  986 dtrace_getnanotime(struct timespec *tsp)
  987 {
  988         struct timehands *th;
  989         u_int gen;
  990 
  991         do {
  992                 th = timehands;
  993                 gen = th->th_generation;
  994                 *tsp = th->th_nanotime;
  995         } while (gen == 0 || gen != th->th_generation);
  996 }
  997 
  998 /*
  999  * System clock currently providing time to the system. Modifiable via sysctl
 1000  * when the FFCLOCK option is defined.
 1001  */
 1002 int sysclock_active = SYSCLOCK_FBCK;
 1003 
 1004 /* Internal NTP status and error estimates. */
 1005 extern int time_status;
 1006 extern long time_esterror;
 1007 
 1008 /*
 1009  * Take a snapshot of sysclock data which can be used to compare system clocks
 1010  * and generate timestamps after the fact.
 1011  */
 1012 void
 1013 sysclock_getsnapshot(struct sysclock_snap *clock_snap, int fast)
 1014 {
 1015         struct fbclock_info *fbi;
 1016         struct timehands *th;
 1017         struct bintime bt;
 1018         unsigned int delta, gen;
 1019 #ifdef FFCLOCK
 1020         ffcounter ffcount;
 1021         struct fftimehands *ffth;
 1022         struct ffclock_info *ffi;
 1023         struct ffclock_estimate cest;
 1024 
 1025         ffi = &clock_snap->ff_info;
 1026 #endif
 1027 
 1028         fbi = &clock_snap->fb_info;
 1029         delta = 0;
 1030 
 1031         do {
 1032                 th = timehands;
 1033                 gen = th->th_generation;
 1034                 fbi->th_scale = th->th_scale;
 1035                 fbi->tick_time = th->th_offset;
 1036 #ifdef FFCLOCK
 1037                 ffth = fftimehands;
 1038                 ffi->tick_time = ffth->tick_time_lerp;
 1039                 ffi->tick_time_lerp = ffth->tick_time_lerp;
 1040                 ffi->period = ffth->cest.period;
 1041                 ffi->period_lerp = ffth->period_lerp;
 1042                 clock_snap->ffcount = ffth->tick_ffcount;
 1043                 cest = ffth->cest;
 1044 #endif
 1045                 if (!fast)
 1046                         delta = tc_delta(th);
 1047         } while (gen == 0 || gen != th->th_generation);
 1048 
 1049         clock_snap->delta = delta;
 1050         clock_snap->sysclock_active = sysclock_active;
 1051 
 1052         /* Record feedback clock status and error. */
 1053         clock_snap->fb_info.status = time_status;
 1054         /* XXX: Very crude estimate of feedback clock error. */
 1055         bt.sec = time_esterror / 1000000;
 1056         bt.frac = ((time_esterror - bt.sec) * 1000000) *
 1057             (uint64_t)18446744073709ULL;
 1058         clock_snap->fb_info.error = bt;
 1059 
 1060 #ifdef FFCLOCK
 1061         if (!fast)
 1062                 clock_snap->ffcount += delta;
 1063 
 1064         /* Record feed-forward clock leap second adjustment. */
 1065         ffi->leapsec_adjustment = cest.leapsec_total;
 1066         if (clock_snap->ffcount > cest.leapsec_next)
 1067                 ffi->leapsec_adjustment -= cest.leapsec;
 1068 
 1069         /* Record feed-forward clock status and error. */
 1070         clock_snap->ff_info.status = cest.status;
 1071         ffcount = clock_snap->ffcount - cest.update_ffcount;
 1072         ffclock_convert_delta(ffcount, cest.period, &bt);
 1073         /* 18446744073709 = int(2^64/1e12), err_bound_rate in [ps/s]. */
 1074         bintime_mul(&bt, cest.errb_rate * (uint64_t)18446744073709ULL);
 1075         /* 18446744073 = int(2^64 / 1e9), since err_abs in [ns]. */
 1076         bintime_addx(&bt, cest.errb_abs * (uint64_t)18446744073ULL);
 1077         clock_snap->ff_info.error = bt;
 1078 #endif
 1079 }
 1080 
 1081 /*
 1082  * Convert a sysclock snapshot into a struct bintime based on the specified
 1083  * clock source and flags.
 1084  */
 1085 int
 1086 sysclock_snap2bintime(struct sysclock_snap *cs, struct bintime *bt,
 1087     int whichclock, uint32_t flags)
 1088 {
 1089 #ifdef FFCLOCK
 1090         struct bintime bt2;
 1091         uint64_t period;
 1092 #endif
 1093 
 1094         switch (whichclock) {
 1095         case SYSCLOCK_FBCK:
 1096                 *bt = cs->fb_info.tick_time;
 1097 
 1098                 /* If snapshot was created with !fast, delta will be >0. */
 1099                 if (cs->delta > 0)
 1100                         bintime_addx(bt, cs->fb_info.th_scale * cs->delta);
 1101 
 1102                 if ((flags & FBCLOCK_UPTIME) == 0)
 1103                         bintime_add(bt, &boottimebin);
 1104                 break;
 1105 #ifdef FFCLOCK
 1106         case SYSCLOCK_FFWD:
 1107                 if (flags & FFCLOCK_LERP) {
 1108                         *bt = cs->ff_info.tick_time_lerp;
 1109                         period = cs->ff_info.period_lerp;
 1110                 } else {
 1111                         *bt = cs->ff_info.tick_time;
 1112                         period = cs->ff_info.period;
 1113                 }
 1114 
 1115                 /* If snapshot was created with !fast, delta will be >0. */
 1116                 if (cs->delta > 0) {
 1117                         ffclock_convert_delta(cs->delta, period, &bt2);
 1118                         bintime_add(bt, &bt2);
 1119                 }
 1120 
 1121                 /* Leap second adjustment. */
 1122                 if (flags & FFCLOCK_LEAPSEC)
 1123                         bt->sec -= cs->ff_info.leapsec_adjustment;
 1124 
 1125                 /* Boot time adjustment, for uptime/monotonic clocks. */
 1126                 if (flags & FFCLOCK_UPTIME)
 1127                         bintime_sub(bt, &ffclock_boottime);
 1128                 break;
 1129 #endif
 1130         default:
 1131                 return (EINVAL);
 1132                 break;
 1133         }
 1134 
 1135         return (0);
 1136 }
 1137 
 1138 /*
 1139  * Initialize a new timecounter and possibly use it.
 1140  */
 1141 void
 1142 tc_init(struct timecounter *tc)
 1143 {
 1144         u_int u;
 1145         struct sysctl_oid *tc_root;
 1146 
 1147         u = tc->tc_frequency / tc->tc_counter_mask;
 1148         /* XXX: We need some margin here, 10% is a guess */
 1149         u *= 11;
 1150         u /= 10;
 1151         if (u > hz && tc->tc_quality >= 0) {
 1152                 tc->tc_quality = -2000;
 1153                 if (bootverbose) {
 1154                         printf("Timecounter \"%s\" frequency %ju Hz",
 1155                             tc->tc_name, (uintmax_t)tc->tc_frequency);
 1156                         printf(" -- Insufficient hz, needs at least %u\n", u);
 1157                 }
 1158         } else if (tc->tc_quality >= 0 || bootverbose) {
 1159                 printf("Timecounter \"%s\" frequency %ju Hz quality %d\n",
 1160                     tc->tc_name, (uintmax_t)tc->tc_frequency,
 1161                     tc->tc_quality);
 1162         }
 1163 
 1164         tc->tc_next = timecounters;
 1165         timecounters = tc;
 1166         /*
 1167          * Set up sysctl tree for this counter.
 1168          */
 1169         tc_root = SYSCTL_ADD_NODE(NULL,
 1170             SYSCTL_STATIC_CHILDREN(_kern_timecounter_tc), OID_AUTO, tc->tc_name,
 1171             CTLFLAG_RW, 0, "timecounter description");
 1172         SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
 1173             "mask", CTLFLAG_RD, &(tc->tc_counter_mask), 0,
 1174             "mask for implemented bits");
 1175         SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
 1176             "counter", CTLTYPE_UINT | CTLFLAG_RD, tc, sizeof(*tc),
 1177             sysctl_kern_timecounter_get, "IU", "current timecounter value");
 1178         SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
 1179             "frequency", CTLTYPE_U64 | CTLFLAG_RD, tc, sizeof(*tc),
 1180              sysctl_kern_timecounter_freq, "QU", "timecounter frequency");
 1181         SYSCTL_ADD_INT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
 1182             "quality", CTLFLAG_RD, &(tc->tc_quality), 0,
 1183             "goodness of time counter");
 1184         /*
 1185          * Never automatically use a timecounter with negative quality.
 1186          * Even though we run on the dummy counter, switching here may be
 1187          * worse since this timecounter may not be monotonous.
 1188          */
 1189         if (tc->tc_quality < 0)
 1190                 return;
 1191         if (tc->tc_quality < timecounter->tc_quality)
 1192                 return;
 1193         if (tc->tc_quality == timecounter->tc_quality &&
 1194             tc->tc_frequency < timecounter->tc_frequency)
 1195                 return;
 1196         (void)tc->tc_get_timecount(tc);
 1197         (void)tc->tc_get_timecount(tc);
 1198         timecounter = tc;
 1199 }
 1200 
 1201 /* Report the frequency of the current timecounter. */
 1202 uint64_t
 1203 tc_getfrequency(void)
 1204 {
 1205 
 1206         return (timehands->th_counter->tc_frequency);
 1207 }
 1208 
 1209 /*
 1210  * Step our concept of UTC.  This is done by modifying our estimate of
 1211  * when we booted.
 1212  * XXX: not locked.
 1213  */
 1214 void
 1215 tc_setclock(struct timespec *ts)
 1216 {
 1217         struct timespec tbef, taft;
 1218         struct bintime bt, bt2;
 1219 
 1220         cpu_tick_calibrate(1);
 1221         nanotime(&tbef);
 1222         timespec2bintime(ts, &bt);
 1223         binuptime(&bt2);
 1224         bintime_sub(&bt, &bt2);
 1225         bintime_add(&bt2, &boottimebin);
 1226         boottimebin = bt;
 1227         bintime2timeval(&bt, &boottime);
 1228 
 1229         /* XXX fiddle all the little crinkly bits around the fiords... */
 1230         tc_windup();
 1231         nanotime(&taft);
 1232         if (timestepwarnings) {
 1233                 log(LOG_INFO,
 1234                     "Time stepped from %jd.%09ld to %jd.%09ld (%jd.%09ld)\n",
 1235                     (intmax_t)tbef.tv_sec, tbef.tv_nsec,
 1236                     (intmax_t)taft.tv_sec, taft.tv_nsec,
 1237                     (intmax_t)ts->tv_sec, ts->tv_nsec);
 1238         }
 1239         cpu_tick_calibrate(1);
 1240 }
 1241 
 1242 /*
 1243  * Initialize the next struct timehands in the ring and make
 1244  * it the active timehands.  Along the way we might switch to a different
 1245  * timecounter and/or do seconds processing in NTP.  Slightly magic.
 1246  */
 1247 static void
 1248 tc_windup(void)
 1249 {
 1250         struct bintime bt;
 1251         struct timehands *th, *tho;
 1252         uint64_t scale;
 1253         u_int delta, ncount, ogen;
 1254         int i;
 1255         time_t t;
 1256 
 1257         /*
 1258          * Make the next timehands a copy of the current one, but do not
 1259          * overwrite the generation or next pointer.  While we update
 1260          * the contents, the generation must be zero.
 1261          */
 1262         tho = timehands;
 1263         th = tho->th_next;
 1264         ogen = th->th_generation;
 1265         th->th_generation = 0;
 1266         bcopy(tho, th, offsetof(struct timehands, th_generation));
 1267 
 1268         /*
 1269          * Capture a timecounter delta on the current timecounter and if
 1270          * changing timecounters, a counter value from the new timecounter.
 1271          * Update the offset fields accordingly.
 1272          */
 1273         delta = tc_delta(th);
 1274         if (th->th_counter != timecounter)
 1275                 ncount = timecounter->tc_get_timecount(timecounter);
 1276         else
 1277                 ncount = 0;
 1278 #ifdef FFCLOCK
 1279         ffclock_windup(delta);
 1280 #endif
 1281         th->th_offset_count += delta;
 1282         th->th_offset_count &= th->th_counter->tc_counter_mask;
 1283         while (delta > th->th_counter->tc_frequency) {
 1284                 /* Eat complete unadjusted seconds. */
 1285                 delta -= th->th_counter->tc_frequency;
 1286                 th->th_offset.sec++;
 1287         }
 1288         if ((delta > th->th_counter->tc_frequency / 2) &&
 1289             (th->th_scale * delta < ((uint64_t)1 << 63))) {
 1290                 /* The product th_scale * delta just barely overflows. */
 1291                 th->th_offset.sec++;
 1292         }
 1293         bintime_addx(&th->th_offset, th->th_scale * delta);
 1294 
 1295         /*
 1296          * Hardware latching timecounters may not generate interrupts on
 1297          * PPS events, so instead we poll them.  There is a finite risk that
 1298          * the hardware might capture a count which is later than the one we
 1299          * got above, and therefore possibly in the next NTP second which might
 1300          * have a different rate than the current NTP second.  It doesn't
 1301          * matter in practice.
 1302          */
 1303         if (tho->th_counter->tc_poll_pps)
 1304                 tho->th_counter->tc_poll_pps(tho->th_counter);
 1305 
 1306         /*
 1307          * Deal with NTP second processing.  The for loop normally
 1308          * iterates at most once, but in extreme situations it might
 1309          * keep NTP sane if timeouts are not run for several seconds.
 1310          * At boot, the time step can be large when the TOD hardware
 1311          * has been read, so on really large steps, we call
 1312          * ntp_update_second only twice.  We need to call it twice in
 1313          * case we missed a leap second.
 1314          */
 1315         bt = th->th_offset;
 1316         bintime_add(&bt, &boottimebin);
 1317         i = bt.sec - tho->th_microtime.tv_sec;
 1318         if (i > LARGE_STEP)
 1319                 i = 2;
 1320         for (; i > 0; i--) {
 1321                 t = bt.sec;
 1322                 ntp_update_second(&th->th_adjustment, &bt.sec);
 1323                 if (bt.sec != t)
 1324                         boottimebin.sec += bt.sec - t;
 1325         }
 1326         /* Update the UTC timestamps used by the get*() functions. */
 1327         /* XXX shouldn't do this here.  Should force non-`get' versions. */
 1328         bintime2timeval(&bt, &th->th_microtime);
 1329         bintime2timespec(&bt, &th->th_nanotime);
 1330 
 1331         /* Now is a good time to change timecounters. */
 1332         if (th->th_counter != timecounter) {
 1333 #ifndef __arm__
 1334                 if ((timecounter->tc_flags & TC_FLAGS_C3STOP) != 0)
 1335                         cpu_disable_deep_sleep++;
 1336                 if ((th->th_counter->tc_flags & TC_FLAGS_C3STOP) != 0)
 1337                         cpu_disable_deep_sleep--;
 1338 #endif
 1339                 th->th_counter = timecounter;
 1340                 th->th_offset_count = ncount;
 1341                 tc_min_ticktock_freq = max(1, timecounter->tc_frequency /
 1342                     (((uint64_t)timecounter->tc_counter_mask + 1) / 3));
 1343 #ifdef FFCLOCK
 1344                 ffclock_change_tc(th);
 1345 #endif
 1346         }
 1347 
 1348         /*-
 1349          * Recalculate the scaling factor.  We want the number of 1/2^64
 1350          * fractions of a second per period of the hardware counter, taking
 1351          * into account the th_adjustment factor which the NTP PLL/adjtime(2)
 1352          * processing provides us with.
 1353          *
 1354          * The th_adjustment is nanoseconds per second with 32 bit binary
 1355          * fraction and we want 64 bit binary fraction of second:
 1356          *
 1357          *       x = a * 2^32 / 10^9 = a * 4.294967296
 1358          *
 1359          * The range of th_adjustment is +/- 5000PPM so inside a 64bit int
 1360          * we can only multiply by about 850 without overflowing, that
 1361          * leaves no suitably precise fractions for multiply before divide.
 1362          *
 1363          * Divide before multiply with a fraction of 2199/512 results in a
 1364          * systematic undercompensation of 10PPM of th_adjustment.  On a
 1365          * 5000PPM adjustment this is a 0.05PPM error.  This is acceptable.
 1366          *
 1367          * We happily sacrifice the lowest of the 64 bits of our result
 1368          * to the goddess of code clarity.
 1369          *
 1370          */
 1371         scale = (uint64_t)1 << 63;
 1372         scale += (th->th_adjustment / 1024) * 2199;
 1373         scale /= th->th_counter->tc_frequency;
 1374         th->th_scale = scale * 2;
 1375 
 1376         /*
 1377          * Now that the struct timehands is again consistent, set the new
 1378          * generation number, making sure to not make it zero.
 1379          */
 1380         if (++ogen == 0)
 1381                 ogen = 1;
 1382         th->th_generation = ogen;
 1383 
 1384         /* Go live with the new struct timehands. */
 1385 #ifdef FFCLOCK
 1386         switch (sysclock_active) {
 1387         case SYSCLOCK_FBCK:
 1388 #endif
 1389                 time_second = th->th_microtime.tv_sec;
 1390                 time_uptime = th->th_offset.sec;
 1391 #ifdef FFCLOCK
 1392                 break;
 1393         case SYSCLOCK_FFWD:
 1394                 time_second = fftimehands->tick_time_lerp.sec;
 1395                 time_uptime = fftimehands->tick_time_lerp.sec - ffclock_boottime.sec;
 1396                 break;
 1397         }
 1398 #endif
 1399 
 1400         timehands = th;
 1401         timekeep_push_vdso();
 1402 }
 1403 
 1404 /* Report or change the active timecounter hardware. */
 1405 static int
 1406 sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS)
 1407 {
 1408         char newname[32];
 1409         struct timecounter *newtc, *tc;
 1410         int error;
 1411 
 1412         tc = timecounter;
 1413         strlcpy(newname, tc->tc_name, sizeof(newname));
 1414 
 1415         error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req);
 1416         if (error != 0 || req->newptr == NULL ||
 1417             strcmp(newname, tc->tc_name) == 0)
 1418                 return (error);
 1419         for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
 1420                 if (strcmp(newname, newtc->tc_name) != 0)
 1421                         continue;
 1422 
 1423                 /* Warm up new timecounter. */
 1424                 (void)newtc->tc_get_timecount(newtc);
 1425                 (void)newtc->tc_get_timecount(newtc);
 1426 
 1427                 timecounter = newtc;
 1428                 timekeep_push_vdso();
 1429                 return (0);
 1430         }
 1431         return (EINVAL);
 1432 }
 1433 
 1434 SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware, CTLTYPE_STRING | CTLFLAG_RW,
 1435     0, 0, sysctl_kern_timecounter_hardware, "A",
 1436     "Timecounter hardware selected");
 1437 
 1438 
 1439 /* Report or change the active timecounter hardware. */
 1440 static int
 1441 sysctl_kern_timecounter_choice(SYSCTL_HANDLER_ARGS)
 1442 {
 1443         char buf[32], *spc;
 1444         struct timecounter *tc;
 1445         int error;
 1446 
 1447         spc = "";
 1448         error = 0;
 1449         for (tc = timecounters; error == 0 && tc != NULL; tc = tc->tc_next) {
 1450                 sprintf(buf, "%s%s(%d)",
 1451                     spc, tc->tc_name, tc->tc_quality);
 1452                 error = SYSCTL_OUT(req, buf, strlen(buf));
 1453                 spc = " ";
 1454         }
 1455         return (error);
 1456 }
 1457 
 1458 SYSCTL_PROC(_kern_timecounter, OID_AUTO, choice, CTLTYPE_STRING | CTLFLAG_RD,
 1459     0, 0, sysctl_kern_timecounter_choice, "A", "Timecounter hardware detected");
 1460 
 1461 /*
 1462  * RFC 2783 PPS-API implementation.
 1463  */
 1464 
 1465 static int
 1466 pps_fetch(struct pps_fetch_args *fapi, struct pps_state *pps)
 1467 {
 1468         int err, timo;
 1469         pps_seq_t aseq, cseq;
 1470         struct timeval tv;
 1471 
 1472         if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
 1473                 return (EINVAL);
 1474 
 1475         /*
 1476          * If no timeout is requested, immediately return whatever values were
 1477          * most recently captured.  If timeout seconds is -1, that's a request
 1478          * to block without a timeout.  WITNESS won't let us sleep forever
 1479          * without a lock (we really don't need a lock), so just repeatedly
 1480          * sleep a long time.
 1481          */
 1482         if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec) {
 1483                 if (fapi->timeout.tv_sec == -1)
 1484                         timo = 0x7fffffff;
 1485                 else {
 1486                         tv.tv_sec = fapi->timeout.tv_sec;
 1487                         tv.tv_usec = fapi->timeout.tv_nsec / 1000;
 1488                         timo = tvtohz(&tv);
 1489                 }
 1490                 aseq = pps->ppsinfo.assert_sequence;
 1491                 cseq = pps->ppsinfo.clear_sequence;
 1492                 while (aseq == pps->ppsinfo.assert_sequence &&
 1493                     cseq == pps->ppsinfo.clear_sequence) {
 1494                         err = tsleep(pps, PCATCH, "ppsfch", timo);
 1495                         if (err == EWOULDBLOCK && fapi->timeout.tv_sec == -1) {
 1496                                 continue;
 1497                         } else if (err != 0) {
 1498                                 return (err);
 1499                         }
 1500                 }
 1501         }
 1502 
 1503         pps->ppsinfo.current_mode = pps->ppsparam.mode;
 1504         fapi->pps_info_buf = pps->ppsinfo;
 1505 
 1506         return (0);
 1507 }
 1508 
 1509 int
 1510 pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
 1511 {
 1512         pps_params_t *app;
 1513         struct pps_fetch_args *fapi;
 1514 #ifdef FFCLOCK
 1515         struct pps_fetch_ffc_args *fapi_ffc;
 1516 #endif
 1517 #ifdef PPS_SYNC
 1518         struct pps_kcbind_args *kapi;
 1519 #endif
 1520 
 1521         KASSERT(pps != NULL, ("NULL pps pointer in pps_ioctl"));
 1522         switch (cmd) {
 1523         case PPS_IOC_CREATE:
 1524                 return (0);
 1525         case PPS_IOC_DESTROY:
 1526                 return (0);
 1527         case PPS_IOC_SETPARAMS:
 1528                 app = (pps_params_t *)data;
 1529                 if (app->mode & ~pps->ppscap)
 1530                         return (EINVAL);
 1531 #ifdef FFCLOCK
 1532                 /* Ensure only a single clock is selected for ffc timestamp. */
 1533                 if ((app->mode & PPS_TSCLK_MASK) == PPS_TSCLK_MASK)
 1534                         return (EINVAL);
 1535 #endif
 1536                 pps->ppsparam = *app;
 1537                 return (0);
 1538         case PPS_IOC_GETPARAMS:
 1539                 app = (pps_params_t *)data;
 1540                 *app = pps->ppsparam;
 1541                 app->api_version = PPS_API_VERS_1;
 1542                 return (0);
 1543         case PPS_IOC_GETCAP:
 1544                 *(int*)data = pps->ppscap;
 1545                 return (0);
 1546         case PPS_IOC_FETCH:
 1547                 fapi = (struct pps_fetch_args *)data;
 1548                 return (pps_fetch(fapi, pps));
 1549 #ifdef FFCLOCK
 1550         case PPS_IOC_FETCH_FFCOUNTER:
 1551                 fapi_ffc = (struct pps_fetch_ffc_args *)data;
 1552                 if (fapi_ffc->tsformat && fapi_ffc->tsformat !=
 1553                     PPS_TSFMT_TSPEC)
 1554                         return (EINVAL);
 1555                 if (fapi_ffc->timeout.tv_sec || fapi_ffc->timeout.tv_nsec)
 1556                         return (EOPNOTSUPP);
 1557                 pps->ppsinfo_ffc.current_mode = pps->ppsparam.mode;
 1558                 fapi_ffc->pps_info_buf_ffc = pps->ppsinfo_ffc;
 1559                 /* Overwrite timestamps if feedback clock selected. */
 1560                 switch (pps->ppsparam.mode & PPS_TSCLK_MASK) {
 1561                 case PPS_TSCLK_FBCK:
 1562                         fapi_ffc->pps_info_buf_ffc.assert_timestamp =
 1563                             pps->ppsinfo.assert_timestamp;
 1564                         fapi_ffc->pps_info_buf_ffc.clear_timestamp =
 1565                             pps->ppsinfo.clear_timestamp;
 1566                         break;
 1567                 case PPS_TSCLK_FFWD:
 1568                         break;
 1569                 default:
 1570                         break;
 1571                 }
 1572                 return (0);
 1573 #endif /* FFCLOCK */
 1574         case PPS_IOC_KCBIND:
 1575 #ifdef PPS_SYNC
 1576                 kapi = (struct pps_kcbind_args *)data;
 1577                 /* XXX Only root should be able to do this */
 1578                 if (kapi->tsformat && kapi->tsformat != PPS_TSFMT_TSPEC)
 1579                         return (EINVAL);
 1580                 if (kapi->kernel_consumer != PPS_KC_HARDPPS)
 1581                         return (EINVAL);
 1582                 if (kapi->edge & ~pps->ppscap)
 1583                         return (EINVAL);
 1584                 pps->kcmode = kapi->edge;
 1585                 return (0);
 1586 #else
 1587                 return (EOPNOTSUPP);
 1588 #endif
 1589         default:
 1590                 return (ENOIOCTL);
 1591         }
 1592 }
 1593 
 1594 void
 1595 pps_init(struct pps_state *pps)
 1596 {
 1597         pps->ppscap |= PPS_TSFMT_TSPEC | PPS_CANWAIT;
 1598         if (pps->ppscap & PPS_CAPTUREASSERT)
 1599                 pps->ppscap |= PPS_OFFSETASSERT;
 1600         if (pps->ppscap & PPS_CAPTURECLEAR)
 1601                 pps->ppscap |= PPS_OFFSETCLEAR;
 1602 #ifdef FFCLOCK
 1603         pps->ppscap |= PPS_TSCLK_MASK;
 1604 #endif
 1605 }
 1606 
 1607 void
 1608 pps_capture(struct pps_state *pps)
 1609 {
 1610         struct timehands *th;
 1611 
 1612         KASSERT(pps != NULL, ("NULL pps pointer in pps_capture"));
 1613         th = timehands;
 1614         pps->capgen = th->th_generation;
 1615         pps->capth = th;
 1616 #ifdef FFCLOCK
 1617         pps->capffth = fftimehands;
 1618 #endif
 1619         pps->capcount = th->th_counter->tc_get_timecount(th->th_counter);
 1620         if (pps->capgen != th->th_generation)
 1621                 pps->capgen = 0;
 1622 }
 1623 
 1624 void
 1625 pps_event(struct pps_state *pps, int event)
 1626 {
 1627         struct bintime bt;
 1628         struct timespec ts, *tsp, *osp;
 1629         u_int tcount, *pcount;
 1630         int foff, fhard;
 1631         pps_seq_t *pseq;
 1632 #ifdef FFCLOCK
 1633         struct timespec *tsp_ffc;
 1634         pps_seq_t *pseq_ffc;
 1635         ffcounter *ffcount;
 1636 #endif
 1637 
 1638         KASSERT(pps != NULL, ("NULL pps pointer in pps_event"));
 1639         /* If the timecounter was wound up underneath us, bail out. */
 1640         if (pps->capgen == 0 || pps->capgen != pps->capth->th_generation)
 1641                 return;
 1642 
 1643         /* Things would be easier with arrays. */
 1644         if (event == PPS_CAPTUREASSERT) {
 1645                 tsp = &pps->ppsinfo.assert_timestamp;
 1646                 osp = &pps->ppsparam.assert_offset;
 1647                 foff = pps->ppsparam.mode & PPS_OFFSETASSERT;
 1648                 fhard = pps->kcmode & PPS_CAPTUREASSERT;
 1649                 pcount = &pps->ppscount[0];
 1650                 pseq = &pps->ppsinfo.assert_sequence;
 1651 #ifdef FFCLOCK
 1652                 ffcount = &pps->ppsinfo_ffc.assert_ffcount;
 1653                 tsp_ffc = &pps->ppsinfo_ffc.assert_timestamp;
 1654                 pseq_ffc = &pps->ppsinfo_ffc.assert_sequence;
 1655 #endif
 1656         } else {
 1657                 tsp = &pps->ppsinfo.clear_timestamp;
 1658                 osp = &pps->ppsparam.clear_offset;
 1659                 foff = pps->ppsparam.mode & PPS_OFFSETCLEAR;
 1660                 fhard = pps->kcmode & PPS_CAPTURECLEAR;
 1661                 pcount = &pps->ppscount[1];
 1662                 pseq = &pps->ppsinfo.clear_sequence;
 1663 #ifdef FFCLOCK
 1664                 ffcount = &pps->ppsinfo_ffc.clear_ffcount;
 1665                 tsp_ffc = &pps->ppsinfo_ffc.clear_timestamp;
 1666                 pseq_ffc = &pps->ppsinfo_ffc.clear_sequence;
 1667 #endif
 1668         }
 1669 
 1670         /*
 1671          * If the timecounter changed, we cannot compare the count values, so
 1672          * we have to drop the rest of the PPS-stuff until the next event.
 1673          */
 1674         if (pps->ppstc != pps->capth->th_counter) {
 1675                 pps->ppstc = pps->capth->th_counter;
 1676                 *pcount = pps->capcount;
 1677                 pps->ppscount[2] = pps->capcount;
 1678                 return;
 1679         }
 1680 
 1681         /* Convert the count to a timespec. */
 1682         tcount = pps->capcount - pps->capth->th_offset_count;
 1683         tcount &= pps->capth->th_counter->tc_counter_mask;
 1684         bt = pps->capth->th_offset;
 1685         bintime_addx(&bt, pps->capth->th_scale * tcount);
 1686         bintime_add(&bt, &boottimebin);
 1687         bintime2timespec(&bt, &ts);
 1688 
 1689         /* If the timecounter was wound up underneath us, bail out. */
 1690         if (pps->capgen != pps->capth->th_generation)
 1691                 return;
 1692 
 1693         *pcount = pps->capcount;
 1694         (*pseq)++;
 1695         *tsp = ts;
 1696 
 1697         if (foff) {
 1698                 timespecadd(tsp, osp);
 1699                 if (tsp->tv_nsec < 0) {
 1700                         tsp->tv_nsec += 1000000000;
 1701                         tsp->tv_sec -= 1;
 1702                 }
 1703         }
 1704 
 1705 #ifdef FFCLOCK
 1706         *ffcount = pps->capffth->tick_ffcount + tcount;
 1707         bt = pps->capffth->tick_time;
 1708         ffclock_convert_delta(tcount, pps->capffth->cest.period, &bt);
 1709         bintime_add(&bt, &pps->capffth->tick_time);
 1710         bintime2timespec(&bt, &ts);
 1711         (*pseq_ffc)++;
 1712         *tsp_ffc = ts;
 1713 #endif
 1714 
 1715 #ifdef PPS_SYNC
 1716         if (fhard) {
 1717                 uint64_t scale;
 1718 
 1719                 /*
 1720                  * Feed the NTP PLL/FLL.
 1721                  * The FLL wants to know how many (hardware) nanoseconds
 1722                  * elapsed since the previous event.
 1723                  */
 1724                 tcount = pps->capcount - pps->ppscount[2];
 1725                 pps->ppscount[2] = pps->capcount;
 1726                 tcount &= pps->capth->th_counter->tc_counter_mask;
 1727                 scale = (uint64_t)1 << 63;
 1728                 scale /= pps->capth->th_counter->tc_frequency;
 1729                 scale *= 2;
 1730                 bt.sec = 0;
 1731                 bt.frac = 0;
 1732                 bintime_addx(&bt, scale * tcount);
 1733                 bintime2timespec(&bt, &ts);
 1734                 hardpps(tsp, ts.tv_nsec + 1000000000 * ts.tv_sec);
 1735         }
 1736 #endif
 1737 
 1738         /* Wakeup anyone sleeping in pps_fetch().  */
 1739         wakeup(pps);
 1740 }
 1741 
 1742 /*
 1743  * Timecounters need to be updated every so often to prevent the hardware
 1744  * counter from overflowing.  Updating also recalculates the cached values
 1745  * used by the get*() family of functions, so their precision depends on
 1746  * the update frequency.
 1747  */
 1748 
 1749 static int tc_tick;
 1750 SYSCTL_INT(_kern_timecounter, OID_AUTO, tick, CTLFLAG_RD, &tc_tick, 0,
 1751     "Approximate number of hardclock ticks in a millisecond");
 1752 
 1753 void
 1754 tc_ticktock(int cnt)
 1755 {
 1756         static int count;
 1757 
 1758         count += cnt;
 1759         if (count < tc_tick)
 1760                 return;
 1761         count = 0;
 1762         tc_windup();
 1763 }
 1764 
 1765 static void __inline
 1766 tc_adjprecision(void)
 1767 {
 1768         int t;
 1769 
 1770         if (tc_timepercentage > 0) {
 1771                 t = (99 + tc_timepercentage) / tc_timepercentage;
 1772                 tc_precexp = fls(t + (t >> 1)) - 1;
 1773                 FREQ2BT(hz / tc_tick, &bt_timethreshold);
 1774                 FREQ2BT(hz, &bt_tickthreshold);
 1775                 bintime_shift(&bt_timethreshold, tc_precexp);
 1776                 bintime_shift(&bt_tickthreshold, tc_precexp);
 1777         } else {
 1778                 tc_precexp = 31;
 1779                 bt_timethreshold.sec = INT_MAX;
 1780                 bt_timethreshold.frac = ~(uint64_t)0;
 1781                 bt_tickthreshold = bt_timethreshold;
 1782         }
 1783         sbt_timethreshold = bttosbt(bt_timethreshold);
 1784         sbt_tickthreshold = bttosbt(bt_tickthreshold);
 1785 }
 1786 
 1787 static int
 1788 sysctl_kern_timecounter_adjprecision(SYSCTL_HANDLER_ARGS)
 1789 {
 1790         int error, val;
 1791 
 1792         val = tc_timepercentage;
 1793         error = sysctl_handle_int(oidp, &val, 0, req);
 1794         if (error != 0 || req->newptr == NULL)
 1795                 return (error);
 1796         tc_timepercentage = val;
 1797         tc_adjprecision();
 1798         return (0);
 1799 }
 1800 
 1801 static void
 1802 inittimecounter(void *dummy)
 1803 {
 1804         u_int p;
 1805         int tick_rate;
 1806 
 1807         /*
 1808          * Set the initial timeout to
 1809          * max(1, <approx. number of hardclock ticks in a millisecond>).
 1810          * People should probably not use the sysctl to set the timeout
 1811          * to smaller than its inital value, since that value is the
 1812          * smallest reasonable one.  If they want better timestamps they
 1813          * should use the non-"get"* functions.
 1814          */
 1815         if (hz > 1000)
 1816                 tc_tick = (hz + 500) / 1000;
 1817         else
 1818                 tc_tick = 1;
 1819         tc_adjprecision();
 1820         FREQ2BT(hz, &tick_bt);
 1821         tick_sbt = bttosbt(tick_bt);
 1822         tick_rate = hz / tc_tick;
 1823         FREQ2BT(tick_rate, &tc_tick_bt);
 1824         tc_tick_sbt = bttosbt(tc_tick_bt);
 1825         p = (tc_tick * 1000000) / hz;
 1826         printf("Timecounters tick every %d.%03u msec\n", p / 1000, p % 1000);
 1827 
 1828 #ifdef FFCLOCK
 1829         ffclock_init();
 1830 #endif
 1831         /* warm up new timecounter (again) and get rolling. */
 1832         (void)timecounter->tc_get_timecount(timecounter);
 1833         (void)timecounter->tc_get_timecount(timecounter);
 1834         tc_windup();
 1835 }
 1836 
 1837 SYSINIT(timecounter, SI_SUB_CLOCKS, SI_ORDER_SECOND, inittimecounter, NULL);
 1838 
 1839 /* Cpu tick handling -------------------------------------------------*/
 1840 
 1841 static int cpu_tick_variable;
 1842 static uint64_t cpu_tick_frequency;
 1843 
 1844 static uint64_t
 1845 tc_cpu_ticks(void)
 1846 {
 1847         static uint64_t base;
 1848         static unsigned last;
 1849         unsigned u;
 1850         struct timecounter *tc;
 1851 
 1852         tc = timehands->th_counter;
 1853         u = tc->tc_get_timecount(tc) & tc->tc_counter_mask;
 1854         if (u < last)
 1855                 base += (uint64_t)tc->tc_counter_mask + 1;
 1856         last = u;
 1857         return (u + base);
 1858 }
 1859 
 1860 void
 1861 cpu_tick_calibration(void)
 1862 {
 1863         static time_t last_calib;
 1864 
 1865         if (time_uptime != last_calib && !(time_uptime & 0xf)) {
 1866                 cpu_tick_calibrate(0);
 1867                 last_calib = time_uptime;
 1868         }
 1869 }
 1870 
 1871 /*
 1872  * This function gets called every 16 seconds on only one designated
 1873  * CPU in the system from hardclock() via cpu_tick_calibration()().
 1874  *
 1875  * Whenever the real time clock is stepped we get called with reset=1
 1876  * to make sure we handle suspend/resume and similar events correctly.
 1877  */
 1878 
 1879 static void
 1880 cpu_tick_calibrate(int reset)
 1881 {
 1882         static uint64_t c_last;
 1883         uint64_t c_this, c_delta;
 1884         static struct bintime  t_last;
 1885         struct bintime t_this, t_delta;
 1886         uint32_t divi;
 1887 
 1888         if (reset) {
 1889                 /* The clock was stepped, abort & reset */
 1890                 t_last.sec = 0;
 1891                 return;
 1892         }
 1893 
 1894         /* we don't calibrate fixed rate cputicks */
 1895         if (!cpu_tick_variable)
 1896                 return;
 1897 
 1898         getbinuptime(&t_this);
 1899         c_this = cpu_ticks();
 1900         if (t_last.sec != 0) {
 1901                 c_delta = c_this - c_last;
 1902                 t_delta = t_this;
 1903                 bintime_sub(&t_delta, &t_last);
 1904                 /*
 1905                  * Headroom:
 1906                  *      2^(64-20) / 16[s] =
 1907                  *      2^(44) / 16[s] =
 1908                  *      17.592.186.044.416 / 16 =
 1909                  *      1.099.511.627.776 [Hz]
 1910                  */
 1911                 divi = t_delta.sec << 20;
 1912                 divi |= t_delta.frac >> (64 - 20);
 1913                 c_delta <<= 20;
 1914                 c_delta /= divi;
 1915                 if (c_delta > cpu_tick_frequency) {
 1916                         if (0 && bootverbose)
 1917                                 printf("cpu_tick increased to %ju Hz\n",
 1918                                     c_delta);
 1919                         cpu_tick_frequency = c_delta;
 1920                 }
 1921         }
 1922         c_last = c_this;
 1923         t_last = t_this;
 1924 }
 1925 
 1926 void
 1927 set_cputicker(cpu_tick_f *func, uint64_t freq, unsigned var)
 1928 {
 1929 
 1930         if (func == NULL) {
 1931                 cpu_ticks = tc_cpu_ticks;
 1932         } else {
 1933                 cpu_tick_frequency = freq;
 1934                 cpu_tick_variable = var;
 1935                 cpu_ticks = func;
 1936         }
 1937 }
 1938 
 1939 uint64_t
 1940 cpu_tickrate(void)
 1941 {
 1942 
 1943         if (cpu_ticks == tc_cpu_ticks) 
 1944                 return (tc_getfrequency());
 1945         return (cpu_tick_frequency);
 1946 }
 1947 
 1948 /*
 1949  * We need to be slightly careful converting cputicks to microseconds.
 1950  * There is plenty of margin in 64 bits of microseconds (half a million
 1951  * years) and in 64 bits at 4 GHz (146 years), but if we do a multiply
 1952  * before divide conversion (to retain precision) we find that the
 1953  * margin shrinks to 1.5 hours (one millionth of 146y).
 1954  * With a three prong approach we never lose significant bits, no
 1955  * matter what the cputick rate and length of timeinterval is.
 1956  */
 1957 
 1958 uint64_t
 1959 cputick2usec(uint64_t tick)
 1960 {
 1961 
 1962         if (tick > 18446744073709551LL)         /* floor(2^64 / 1000) */
 1963                 return (tick / (cpu_tickrate() / 1000000LL));
 1964         else if (tick > 18446744073709LL)       /* floor(2^64 / 1000000) */
 1965                 return ((tick * 1000LL) / (cpu_tickrate() / 1000LL));
 1966         else
 1967                 return ((tick * 1000000LL) / cpu_tickrate());
 1968 }
 1969 
 1970 cpu_tick_f      *cpu_ticks = tc_cpu_ticks;
 1971 
 1972 static int vdso_th_enable = 1;
 1973 static int
 1974 sysctl_fast_gettime(SYSCTL_HANDLER_ARGS)
 1975 {
 1976         int old_vdso_th_enable, error;
 1977 
 1978         old_vdso_th_enable = vdso_th_enable;
 1979         error = sysctl_handle_int(oidp, &old_vdso_th_enable, 0, req);
 1980         if (error != 0)
 1981                 return (error);
 1982         vdso_th_enable = old_vdso_th_enable;
 1983         timekeep_push_vdso();
 1984         return (0);
 1985 }
 1986 SYSCTL_PROC(_kern_timecounter, OID_AUTO, fast_gettime,
 1987     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
 1988     NULL, 0, sysctl_fast_gettime, "I", "Enable fast time of day");
 1989 
 1990 uint32_t
 1991 tc_fill_vdso_timehands(struct vdso_timehands *vdso_th)
 1992 {
 1993         struct timehands *th;
 1994         uint32_t enabled;
 1995 
 1996         th = timehands;
 1997         vdso_th->th_algo = VDSO_TH_ALGO_1;
 1998         vdso_th->th_scale = th->th_scale;
 1999         vdso_th->th_offset_count = th->th_offset_count;
 2000         vdso_th->th_counter_mask = th->th_counter->tc_counter_mask;
 2001         vdso_th->th_offset = th->th_offset;
 2002         vdso_th->th_boottime = boottimebin;
 2003         enabled = cpu_fill_vdso_timehands(vdso_th);
 2004         if (!vdso_th_enable)
 2005                 enabled = 0;
 2006         return (enabled);
 2007 }
 2008 
 2009 #ifdef COMPAT_FREEBSD32
 2010 uint32_t
 2011 tc_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32)
 2012 {
 2013         struct timehands *th;
 2014         uint32_t enabled;
 2015 
 2016         th = timehands;
 2017         vdso_th32->th_algo = VDSO_TH_ALGO_1;
 2018         *(uint64_t *)&vdso_th32->th_scale[0] = th->th_scale;
 2019         vdso_th32->th_offset_count = th->th_offset_count;
 2020         vdso_th32->th_counter_mask = th->th_counter->tc_counter_mask;
 2021         vdso_th32->th_offset.sec = th->th_offset.sec;
 2022         *(uint64_t *)&vdso_th32->th_offset.frac[0] = th->th_offset.frac;
 2023         vdso_th32->th_boottime.sec = boottimebin.sec;
 2024         *(uint64_t *)&vdso_th32->th_boottime.frac[0] = boottimebin.frac;
 2025         enabled = cpu_fill_vdso_timehands32(vdso_th32);
 2026         if (!vdso_th_enable)
 2027                 enabled = 0;
 2028         return (enabled);
 2029 }
 2030 #endif

Cache object: 8695a0ba322ae2a63e0d1a1cb50b917a


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.